Method for drilling holes and optionally inserting fasteners

ABSTRACT

The method and apparatus for drilling holes and optionally inserting fasteners of the present invention provide for efficiently drilling holes through a multiple-layer structure because the layers are securely held together during the drilling by an electromagnet and a clamp, each on opposite sides of the structure. The electromagnet and clamp hold the layers together so tightly that burrs do not form within the holes and debris does not accumulate between the layers and, therefore the layers do not have to be disassembled after drilling. In addition, the apparatus and method of the present invention provide for initially drilling the hole with a countersink and for inserting a fastener into the hole, through the electromagnet, immediately after drilling the hole, such that the hole does not have to be revisited after reassembly and drying of the sealant in order to drill a countersink and/or insert a fastener.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional of U.S. application Ser. No.10/158,285, filed May 30, 2002, which is hereby incorporated herein inits entirety by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to enabling an operator to drillholes and optionally insert fasteners, and, in particular to drillingholes and optionally inserting fasteners through multi-layer structuresby utilizing an electromagnet assembly to securely clamp the multi-layerstructure together during the operation.

[0003] The fasteners that hold together multi-layer structures,particularly those structures that are subject to significant dynamicforces and/or pressure over their lifetime, such as aircraft bodies,bridges, vehicle bodies, buildings, and others, must be properly securedin order to ensure that the structure will perform as intended over itslifetime. In order to properly secure a fastener in a multi-layerstructure, the fastener hole must not have any sharp edges, i.e., burrs,there must not be debris between the layers, and any sealant appliedbetween the layers in order to make the structure air and/or water tightmust be sufficiently squeezed out. When excess sealant is presentbetween the layers, the distance between the layers is increased and/oruneven, which may be referred to as a “gasket” condition. Thus, ifburrs, debris and/or excessive sealant are present, then the layerscannot be properly fastened and the layers may suffer corrosion,cracking and/or premature fatigue failure, which generally renders thestructure ineffective for its intended purpose and, therefore, subjectto the expense of repair or replacement.

[0004] Thus, ensuring that a burr-less hole is drilled, that there is nodebris between the layers, and that sealant is properly applied betweenthe layers is an integral part of fastening multi-layer structurestogether. In the aerospace industry, for example, a significant amountof time and labor is expended ensuring that the holes through thesignificant amount of time and labor is expended ensuring that the holesthrough the various layers of the aircraft structure are appropriatelydrilled, cleaned, sealed and fastened. Initially, the layers ofmaterials that form the structure are loosely assembled without sealant,and drill templates are aligned and attached to the structure in theareas to be drilled. A drill operator, guided by the drill template,then drills holes through the layers of materials typically using amanual drill motor. As the hole is being drilled through the layers, thedrill bit tip pushes with the full feed force applied to the drillmotor. This can cause a gap to develop between a drilled layer and thenext layer, particularly when the layers are a stack up of thinmaterial. The gap between the layers causes burrs about the hole anddebris is likely to gather between the layers. Thus, once the holes aredrilled, the layers must be disassembled, the burrs must be removed fromthe holes, and the debris must be cleaned from the surfaces of thelayers, all of which is a time-consuming and labor intensive process.

[0005] Sealant is then applied to the layers prior to re-assembling thelayers. In order to ensure the layers are properly sealed to provide anair and water-tight seal, a generous amount of sealant is applied to thelayers. Clamps that extend through the holes, such as KWIK-LOK™ clampscommercially available from Zephyr Manufacturing Company, Inglewood,Calif., must be placed through each hole of the reassembled layers inorder to squeeze out the sealant to prevent excessive “gasket” betweenthe layers before the sealant dries. The extra sealant squeezes outaround the clamps and must be cleaned from the structure and the clampsduring clamping and/or after the clamps are removed.

[0006] Once the sealant is cured, the clamps may be removed and theholes may be countersunk. In order to countersink a hole, a countersinkdrill bit and microstop countersink cage are attached to the drill motorand the operator revisits each hole to drill the countersink. The holesare then inspected to ensure they were properly countersunk. The holesmay be inspected by checking the countersink of each hole with ameasuring tool, or by installing the fastener to check if it fitsproperly within the hole and countersink. If the holes are satisfactory,then fasteners may be installed and fastened with nuts or swage lockcollars. Overall, this process is expensive, laborious, andtime-consuming. In addition, the integrity of the resulting holesdepends upon the completion of many manual processes, which creates arisk that certain steps may be performed inadequately or completelyoverlooked.

[0007] Therefore, a need exists to drill holes and install fasteners inmulti-layer structures in a more efficient manner, such as by reducingor eliminating the time and expense involved in disassembling thedrilled layers, de-burring the holes, cleaning the debris from thelayers, reassembling the layers, clamping the holes, waiting for thesealant to dry, and revisiting the holes to drill the countersink. Inparticular, there is a need to efficiently drill holes and installfasteners in multi-layer structures in one operation, such that the timeand money involved in the manufacture of multi-layer structures issignificantly reduced.

BRIEF SUMMARY OF THE INVENTION

[0008] The apparatus and method for drilling holes and optionallyinserting fasteners of the present invention reduce the time and expenseinvolved in the manufacture of a multi-layer structure by eliminatingthe need to disassemble the drilled layers in order to de-burr the holesand clean the debris from the layers before reassembling and sealing thelayers and countersinking the holes. The apparatus and method of thisinvention provide for drilling holes, such as countersunk holes, insealed, tightly held layers of a structure and optionally insertingfasteners in the holes such that the process is completed in oneefficient operation. The layers of the structure are held together by anelectromagnet through which a drilling tool may extend and a clamp atleast partially made of magnetic material, such that a hole may bedrilled through the layers without creating burrs or allowing debris toaccumulate between the layers. A fastener may be then immediatelyinserted in the hole.

[0009] The apparatus and method for drilling a hole in a multiple-layerstructure include an electromagnet defining an opening sized to receivea drilling tool and a clamp made of at least partially magneticmaterial, such as a ferrous metal. The electromagnet is positionedproximate the structure such that the opening of the electromagnetdefines the location of the hole to be drilled in the structure. Theclamp is positioned proximate the structure, opposite the electromagnet,such that the electromagnet and the clamp are capable of holding themultiple layer structure together when the electromagnet is energized.The clamp may also define an opening and, if so, the opening of theclamp is aligned with the opening of the electromagnet. A drilling toolmay then be positioned within the opening of the electromagnet in orderto drill a hole through the multiple-layer structure.

[0010] Prior to positioning the electromagnet, the multiple layers ofthe structure may be sealed. While positioning the electromagnet, theelectromagnet opening may be normalized to the portion of the structureto be drilled. The electromagnet may be made of a plurality ofrevolutions of wire and spacers may be located between the revolutionsto facilitate cooling the wire. The electromagnet may be connected to apower source that supplies an electric current, such as an AC and/or DCcurrent, to energize the electromagnet. In order to cool theelectromagnet, at least during the portion of the time that theelectromagnet is energized, air may flow through the electromagnet.

[0011] To align the clamp with the electromagnet, the clamp may becapable of being slidably mounted to the structure, such that the clampmay slide to a position opposite and aligned with the electromagnet. Inaddition, grooves may extend through the clamp in the direction in whichthe clamp is capable of sliding, such that the clamp may slide over thestructure surface without obstruction from previously installedfasteners or other protrusions from the structure. The clamp may includea layer of non-abrasive material on the side of the clamp that faces thestructure for ease of sliding the clamp and to prevent the clamp fromharming the structure while sliding. Furthermore, the electromagnetand/or the clamp may have an alignment indicator to indicate when theopenings of the clamp and the electromagnet are aligned.

[0012] Drilling a hole in the structure may include drilling a holehaving a countersunk portion. To drill a hole with a countersunkportion, the drilling tool may have a first and second portion, wherethe first portion has a diameter that is smaller than the diameter ofthe second portion and the second portion has a length that is greaterthan the length of the opening of the electromagnet.

[0013] The apparatus and method of the present invention may include atemplate positioned on the structure in the location to be drilled, suchthat the opening of the electromagnet is aligned with an opening of thetemplate. The electromagnet may also include a first guidepiece that isaligned with and at least partially defines the opening of theelectromagnet. The opening of the first guidepiece may be smaller thanthe opening of the electromagnet. In addition, the electromagnet mayinclude a second guidepiece opposite the first guidepiece, that also isaligned with and partially defines the opening of the electromagnet. Assuch, if the electromagnet has a first guidepiece, the first guidepiecemay be positioned within the opening of the template to align theopening of the electromagnet with the opening of the template.

[0014] Further embodiments of the apparatus and method of the presentinvention may include a platform that is capable of being positionednear the electromagnet. This platform is referred to as a toolingplatform herein. A rail mounted to the structure may carry the toolingplatform via a transport system, to facilitate gross positioning of thetooling platform, and, thus, the electromagnet relative to thestructure. The tooling platform may have a first opening that is alignedwith the opening in the electromagnet. In addition, the tooling platformmay include a guidepiece that is aligned with and at least partiallydefines the first opening of the tooling platform. The portion of thefirst opening with which the guidepiece is aligned, therefore, may besmaller than other portions of the first opening of the toolingplatform.

[0015] Debris may be removed from the hole as the hole is drilled bycreating air flow through the opening defined by the electromagnet in adirection away from the structure. To remove the debris, the toolingplatform may include a passageway having one end near the first openingof the tooling platform such that debris is pulled through thepassageway while drilling a hole in the structure.

[0016] Advantageous embodiments of the apparatus and method of thepresent invention also provide for the insertion of a fastener in anewly drilled hole. In this regard, air is flowed through the opening ofthe electromagnet. A fastener is placed into the flow of the air and thefastener is carried along in the air flow and is inserted into the hole.Air may be flowed through the opening of the electromagnet by aligning atube with the opening in the electromagnet and pulling air through thetube, such as by means of an air flow generator or compressed air. Theair flow, such as the air flowed through the opening in theelectromagnet, may be laminar air flow. Thus, when the fastener isinserted into the tube, it may be pulled through the tube and thenpushed through the opening of the electromagnet and into the holedrilled in the multiple-layer structure. Furthermore, in embodimentsthat include a tooling platform, the tube may be swivelably attached tothe platform so as to alternately be aligned with and displaced from thefirst opening in the tooling platform.

[0017] The apparatus and method of the present invention also include afastener insertion device and a method of inserting a fastener in a holedefined by a work piece that includes a supply of fasteners, a tube withan opening that is larger than the fastener, and an air flow generator,such as a vacuum source or an air pump, to create air flow in throughthe tube and out toward the work piece. As such, when the tube isaligned with the hole defined in the work piece and the fastener isplaced in the tube, the air carries the fastener through the tube, theninserts it into the hole in the work piece. In some embodiments thefastener may be carried through the tube, through the air flowgenerator, then into the hole in the work piece. Aligning the tubeopening with the work piece hole may include aligning the tube openingwith an opening in a template that is aligned with the work piece hole.The tube may have openings about the circumferential surface of the tubeto prevent the fastener from inhibiting the air flow when it is placedin the tube. In addition, the air flow may be laminar. As such,fasteners may be efficiently inserted in the holes that have beendrilled in the multi-layer structure.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

[0018] Having thus described the invention in general terms, referencewill now be made to the accompanying drawings, which are not necessarilydrawn to scale, and wherein:

[0019]FIG. 1 is a cross-sectional view of an apparatus for drillingholes and optionally inserting fasteners, according to one embodiment ofthe present invention;

[0020]FIG. 2 is a perspective view of an alternative embodiment of anapparatus for drilling holes and optionally inserting fastenersaccording to the present invention;

[0021]FIG. 3 is a perspective view of a transport system connected to aplatform and, in turn, an electromagnet, according to one embodiment ofthe present invention;

[0022]FIG. 4 is cross-sectional view of a further embodiment of anapparatus for drilling holes and optionally inserting fasteners thatincludes a debris removal system, according to one embodiment of thepresent invention;

[0023]FIG. 5 is a cross-sectional view of a fastener insertion systemaccording to one embodiment of the present invention;

[0024]FIG. 6A is a perspective view of an alternative embodiment of afastener insertion system swivelably attached to a platform and in afirst position, according to the present invention; and

[0025]FIG. 6B is a perspective view of the embodiment of the fastenerinsertion system depicted in FIG. 6A in a second position, according tothe present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0026] The present inventions now will be described more fullyhereinafter with reference to the accompanying drawings, in which some,but not all embodiments of the invention are shown. Indeed, theseinventions may be embodied in many different forms and should not beconstrued as limited to the embodiments set forth herein; rather, theseembodiments are provided so that this disclosure will satisfy applicablelegal requirements. Like numbers refer to like elements throughout.

[0027] The method and apparatus for drilling holes and optionallyinserting fasteners of the present invention provide for efficientlydrilling holes through a multiple-layer structure because the layers aresecurely held together during the drilling by an electromagnet and aclamp, each on opposite sides of the structure. The electromagnet andclamp hold the layers together so tightly that the layers do not have tobe disassembled after drilling in order to de-burr the holes and removethe debris from between the layers and, as such, sealant may be appliedprior to drilling and the sealant does not have to dry prior todrilling. In addition, the apparatus and method of the present inventionmay provide for initially drilling the hole with a countersink and forinserting a fastener into the drilled hole, through the electromagnet,immediately after drilling the hole, such that the hole does not have tobe revisited after reassembly of the layers and drying of the sealant inorder to drill a countersink and/or insert a fastener in a separateoperation as is performed in conventional manual installations.

[0028] Multiple layers of materials must be fastened together in manyapplications. For example, portions of buildings, bridges, automobiles,furniture, aircraft, and spacecraft may contain multiple layers oroverlapping layers of material that must be securely fastened together.In the aerospace industry, for instance, the fuselage segments of anaircraft are typically joined together by overlapping the segments or bybutting the segments together and covering the joint with strips ofmaterial and a longeron. In addition, a sealant typically must beapplied to the layers prior to fastening the layers together. In theaerospace industry, for example, a sealant is applied between the layersin order to prevent moisture, which may cause corrosion leading todegradation, eventually resulting in stress cracks and/or fatiguefailure, from collecting between the layers. Only a very thin layer ofsealant should be applied, however, in order to ensure the layers are asclose together as possible. Typically, once the sealant is applied,force is exerted upon the layers in order to squeeze out any excesssealant, as described more fully hereinbelow.

[0029]FIGS. 1 and 4 illustrate an electromagnet 10 and clamp 12 assemblyholding layers of a structure 18 together. FIG. 1 shows theelectromagnet 10 and clamp 12 holding together a butt-joint of astructure 18 that is covered with strips of material 20 and a longeron58, according to one embodiment of the present invention. Theelectromagnet 10 may be formed of a plurality of revolutions of wires 14wrapped about a core of steel. The electromagnet 10 may be connected toa power source that supplies an electric current, such as an AC and/orDC current, to energized the electromagnet. As such, when energized bythe current, the electromagnet attracts any magnetic material, such asferromagnetic material. In addition, when the electromagnet 10 isenergized, the temperature of the wires 14 increases, and theelectromagnet 10 may require cooling, at least during times ofelectromagnet operation. The cooling may occur by generating an air flow15 around the wires 14 of the electromagnet 10. Thus, an air flowgenerator, such as compressed air, may be connected in fluidcommunication with the electromagnet 10 in any manner known to thoseskilled in the art. FIGS. 1 and 4 illustrate the air flow 15 enteringthe electromagnet 10 at one or more apertures 17, but the air flow 15may begin at any other appropriate location. FIG. 2 illustrates oneembodiment of an air flow path 52 around the wires 14 of theelectromagnet by routing the air into and through the electromagnet viatubes 54. Thus, the tubes 54 may connect to the electromagent 10 ataperture 17 or any other appropriate location. In addition, tofacilitate cooling, spacers 16 may be placed between the revolutions ofwires 14. The spacers 16 may be made of any type of material with a highmelting temperature that is also, preferably, non-abrasive andnon-conductive, such as Teflon™, commercially available from du Pont deNemours and Company Corporation, fiberglass, or a weave material.Although the wires may have various shapes, the wires 14 may have asquare-circumferential shape that readily stacks within the spacers 16.Another manner in which the cooling may occur is by pumping fluidthrough a housing of the electromagnet 10 that encloses the wires 14and/or around the wires 14. The pumping system may cool the fluid andwhen the fluid flows through the electromagnet 10, it cools theelectromagnet 10.

[0030] The electromagnet 10 defines an opening 22 typically extendingthrough the center of the electromagnet, through which a drilling tool24 may extend. Thus, the opening 22 of the electromagnet 10 is alignedwith the location on the structure 18 to be drilled. The electromagnet10 may also have at least one guidepiece 26 aligned with and at leastpartially defining the opening 22. Embodiments of the electromagnet 10may include a guidepiece 26 at each end of the opening 22, as shown inFIG. 1, or at only one end of the opening 22. The guidepiece(s) 26 mayextend beyond the opening, be flush with the surface of theelectromagnet 10, or any other position within the opening 22 of theelectromagnet 10. The portion of the opening 22 that is defined by theguidepiece 26 may have a smaller diameter than the other portions of theopening 22. The guidepiece 26 may be a bushing that guides the drillingtool 24 through the opening 22 and prevents side-to-side movement of thedrilling tool 24 while extended through the opening 22. Thus, theguidepiece 26 may be made of a material that is harder than the materialof the drilling tool 24 in order to withstand contact with the drillingtool 24. For example the guidepiece 26 may be made of a hardened steel,such as D2 metal. Additionally, if the electromagnet has a guidepiecefacing the structure, that guidepiece can contact the surface of thestructure to be drilled so as to transfer the force of the electromagnetto a minimized and specific area surrounding the location of the hole tobe drilled.

[0031] In some embodiments of the drilling apparatus, a platform 28,hereinafter referred to as a tooling platform 28 may be attached to theelectromagnet 10 on the side of the electromagnet 10 that is oppositethe structure 18. The tooling platform 28 defines an opening 30 that isaligned with the electromagnet opening 22. In this embodiment, theguidepiece 26, as described above, may be aligned with and at leastpartially define the opening 30. For example, the guidepiece 26 mayextend inwardly from the tooling platform 28 towards the electromagnet10 for insertion within the opening 30 defined by the electromagnet 10.The tooling platform 28 and, in turn, the electromagnet 10 are capableof being controllably moved with respect to the work piece as describedbelow.

[0032] In further embodiments of the present invention, a drillingtemplate 56 may be attached to the structure 18 over the location(s) tobe drilled in order to guide the operator in drilling holes in thecorrect location(s) of the structure 18. The drilling template 56 may beattached to the structure 18 in any manner known to those skilled in theart. One example of attaching the drilling template 56 to the structure18 is by first taping and/or strapping the template to the outside ofthe structure, then loosely aligning all parts involved in the join,such as the strips of material 20 and the longeron 58, using C-clampsand/or tape. A few holes are drilled through the structure 18, thestrips 20, and the longeron 58 (i.e., the parts) using the drillingtemplate 56 and KWIK-LOK™ clamps temporarily affix the template to allof the parts.

[0033] Thus, the operator may position the electromagnet 10, via thetransport system 32, if applicable, as described below, such that theelectromagnet opening 22 is aligned with an opening in the drillingtemplate 56 and, in turn, with the desired drilling location on the workpiece. In those embodiments in which the electromagnet 10 includes aguide piece 26 extending outwardly therefrom toward the template, theguide piece 26 may be sized to fit within the desired opening in thedrilling template 56 to facilitate aligning the electromagnet opening 22with the location to be drilled.

[0034] As shown in FIG. 2, the tooling platform 28 may be attached tothe transport system 32. The transport system 32 facilitates movementand alignment of the platform 28 and, in turn, the electromagnet 10, inrelation to the structure 18. The movement may be controlled by theoperator via at least one handle 50 attached to the tooling platform 28and/or the electromagnet 10. The transport system 32 may move inrelation to the structure 18 by mounting the transport system 32 on arail 44. The rail 44 is generally aligned to be substantially parallelto the location(s) of the holes(s) to be drilled in the structure 18. Ifthe embodiment includes a drilling template 56, as described above, therail 44 may be positioned to be substantially parallel to the top edgeof the drilling template 56 that indicate the location(s) of the hole(s)to be drilled in the structure 18. The rail 44 may be mounted to thestructure 18 by any means known to those skilled in the art. FIG. 2illustrates one embodiment in which the rail is mounted on the structurewith suction cups 46. The air within the suction cups 46 may becontrolled by valve 48, such that once the rail 44 is alignedsubstantially parallel to the location(s) of the hole(s) to be drilledon the structure, air may be removed from the suction cups 46 to securethe rail 44 to the structure 18 by adjusting the valve 48 accordingly.In addition, to remove the secured rail 44 from the structure 18, airmay be added to the suction cups 46 to loosen the suction cups 46 and,therefore, the rail 44, from the structure by adjusting the valve 48accordingly. The transport system 32 is mounted on the rail 44 via railtransport member 42, which is shaped to slidably engage with a portionof the rail 44.

[0035]FIG. 3 depicts a more detailed view of the transport system 32 andthe movements it facilitates. Rail transport member 42 may slide alongthe rail 44 in the directions indicated by arrow 41 in order to move theelectromagnet 10 to an appropriate location on the structure 18 in thedirections indicated by arrow 41. Arm member 34 may also be connected tothe rail transport member 42 at pivot point 36, permitting movement ofthe arm member 34 in relation to the rail transport member 42 in therotational direction designated by arrow 37. Because arm member 34connects the tooling platform 28 to the rest of the transport system 32,movement between arm member 34 and rail transport member 42 in thedirection of arrow 37 facilitates movement of the tooling platform 28and, in turn, the electromagnet 10 away from and toward the structure18. Arm member 34 is also hingedly mounted to the tooling platform 28,permitting movement of the tooling platform 28 in relation to the armmember 34 in the rotational direction designated by arrow 35. Thus,movement between arm member 34 and tooling platform 28 in the directionof arrow 35 facilitate positioning the tooling platform 28 and, in turn,the electromagnet 10, such that the openings 30 and 22 are normal to thesurface 18. If the surface 18 is curved, then the tooling platform 28and, in turn, the electromagnet 10 may be positioned perpendicular to aline tangent to the curvature of surface 18 at the location at which ahole is to drilled. In addition, the hinged connections between armmember 34 and tooling platform 28, and between arm member 34 and railtransport member 42 may cooperate to further facilitate the movementsdescribed above.

[0036] To normalize openings 30 and/or 22 to the structure 18,particularly along a curved surface of the structure 18, the toolingplatform 28 and/or electromagnet 10 may include other features to definethe distance between at least a portion of the tooling platform 28and/or electromagnet 10 and the structure 18. For example, an adjustmentmechanism may serve to define the distance between the tooling platform28 and, therefore, the electromagnet 10, only over the portion of thestructure that curves away from the location of the hole to be drilled,such that the openings 30 and 22 are positioned normal to the drillinglocation.

[0037] Arm member 34 is also capable of moving relative the railtransport member 42 in the directions indicated by arrow 39. Thus,movement between arm member 34 and shafts 40 in the directions of arrow39 facilitate positioning the platform and, in turn, the electromagnet10, over the location on the structure 18 to be drilled. Arm member 34may be attached to shafts 40, and shafts 40 may slidably move throughopenings in housing 47. Housing 47 may contain bushings about theopenings to facilitate sliding of the shafts 40. Caps 43 located at thetop and bottom of shafts 40 serve to prevent arm member 34 from movingmore than a predetermined distance with respect to rail transport member42, and, therefore further controls the movement of tooling platform 28and, in turn, electromagnet 10, in relation to the structure 18. Inaddition, a tension spring may be connected between the top cap ofshafts 40 and spring bracket 38 to facilitate ergonomic movement of thetooling platform 28 and, in turn, the electromagnet 10 by creating acounterbalance force to resist gravity and thereby reduce the forceneeded to position the tooling platform 28 and, in turn, theelectromagnet 10, with respect to the structure 18. Furthermore, thetransport system 32 may include a any type of mechanism known to thoseskilled in the art that allows for a quick connection and disconnectionbetween the tooling platform 28, the electromagnet 10, and the transportsystem 32.

[0038] Prior to, while, or after positioning the electromagnet opening22 in alignment with the location on the structure 18 to be drilled, theclamp 12 may be placed on the opposite side of the structure 18. Theclamp 12 may be at least partially made of a magnetic material, such asa ferrous material, so that when the electromagnet 10 is energized, theelectromagnet 10 and the clamp 12 are attracted together. The clamp 12and electromagnet 10 are placed on opposite sides of the multiple layerstructure 18, such that when the electromagnet 10 is energized andattracts the clamp 12, the layers are tightly held together.

[0039] As FIG. 1 illustrates, the clamp 12 may be shaped to slidablyattach to the structure 18. The clamp 12, therefore, may be shaped toreceive a portion of the structure 18 and to be capable of sliding overany protrusions in the structure. For example, in the aerospaceindustry, the clamp 12 may be shaped to receive a longeron 58 and to becapable of sliding along the longeron 58. In addition, the clamp 12 mayhave recesses 60 through which any existing fasteners in the structuremay pass, thereby permitting the clamp 12 to freely slide. As such, thesurface of the clamp 12 that contacts the structure 18 and longeron 58may be coated with a layer of non-abrasive material, such as Teflon™,commercially available from du Pont de Nemours and Company Corporation,to avoid harming the structure 18 or longeron 58. Alternatively,multiple clamps 12 may be placed along the portion of the structure 18to be drilled, so that the clamps 12 do not need to be slid as often, asfar or at all. In another embodiment, the clamp 12 may be shaped tocover the length of the area of the structure 18 to be drilled, suchthat the clamp 12 does not have to be slid.

[0040] For embodiments of the clamp 12 that must be positioned relativeto the electromagnet, i.e. when the clamp 12 or multiple clamps 12 donot cover the entire area of the structure to be drilled, the clamp 12and electromagnet 10 must be aligned. To align the clamp 12 and theelectromagnet 10, either the clamp 12, the electromagnet 10 or both mayhave an alignment indicator. The alignment indicator presents some typeof signal when the clamp 12 and the electromagnet 10 are properly placedon opposite sides of the work piece relative to each other. For example,a permanent magnet may be placed on the clamp 12 and/or theelectromagnet 10 and the alignment indicator located on the other one ofthe electromagnet 10 and/or the clamp 12 with the alignment indicatorbeing embodied by a magnetic sensor capable of providing a signal, suchas a mechanical movement of a needle or the like, or the illumination ofa light, upon detecting the presence of the magnet.

[0041] Once the clamp 12 is in place, it may be secured to the structure18, such as the longeron 58, by any manner known to those skilled in theart. For instance, the clamp 12 may have two segments that cooperate todefine a recess that is shaped to receive the portion of the structureupon which the clamp 12 rides. The clamp 12 may also include a threadedconnector having a knob 62 that is accessible and may be rotated to movethe two portions of the clamp 12 closer together and to secure the clamp12 on the desired portion of the structure. In another example, the twosegments of the clamp 12 may be hingedly connected, such that when thetwo segments are rotated into alignment with each other about thedesired portion of the structure, the segments may be locked into placeby any manner known to those skilled in the art, such as a spring lock,in order to be secured to the structure.

[0042] When both the electromagnet 10 and the clamp 12 are properlypositioned, the electromagnet may be energized in order to force thelayers of the structure 18 and longeron 58, if appropriate, together.The amount of force exerted upon the layers of the structure 18 andlongeron 58, if appropriate, should be sufficient to prevent the layersfrom moving apart as a drilling tool 24 impinges each layer and shouldbe sufficient to ensure that the sealed layers are as close together aspossible. Thus, the electromagnet 10 and clamp 12 assembly allowsoperators to apply the sealant before drilling the hole in the structureand without having to wait for the sealant to dry because the energizedelectromagnet 10 and clamp 12 hold the layers together tight enough tosqueeze out extra sealant prior to drilling, prevent exit burrs fromforming in the drilled hole, and prevent debris from accumulatingbetween the layers during drilling. Therefore, the electromagnet 10 andclamp 12 assembly reduces the time and expense involved in drillingholes in multiple layer structures, in which the layers otherwise wouldhave to be disassembled and cleaned after drilling, then reassembledwith a fast-drying sealant, the excess of which must be squeezed out andthe remaining sealant dried prior to fastening the layers.

[0043] The electromagnet 10 may be energized by any manner known tothose skilled in the art. Examples include placing an electromagnetpower switch where the operator can easily reach the switch, such as ona handle 50 or the tooling platform 28, to activate a flow of electriccurrent to the electromagnet 10 from a power source. When theelectromagnet 10 is energized, the electromagnet cooling air flow mayalso be activated, as described above. In addition, in some embodiments,a debris removal system may be activated when the electromagnet 10 isenergized. Alternatively, the cooling air flow and/or debris removalsystem may have separate activation switches. As a further alternative,the debris removal system may only be activated when the drill motor 78is activated by monitoring the drill power line.

[0044] The debris removal system may include a air flow source 64 and acollection container 66, as shown in FIG. 2. FIG. 4 illustrates adetailed view of the operation of the debris removal. The air flowsource 64 may be any type of relatively small diameter and high velocityvacuum source, such as a Magnavon pneumatically actuated FOD vacuum bag,commercially available from Magnavon Industries Inc, Placentia, Calif.The air flow source 64 may be attached to a passageway 68 defined orcarried by the tooling platform 28 that extends outwardly from theplatform opening 30. Alternatively, the air flow source 64 may beattached in any manner such that the air flow source 64 may pull debris70 out of the hole being drilled in the structure 18. For example theair flow source 64 may be attached to an opening between the structure18 and the electromagnet 10, an alternate opening in the electromagnet,or an opening between the tooling platform 28 and the electromagnet 10.The air flow source 64 generates air flow 72 from the structure 18 tothe collection container 66. To do this, the air flow source 64 may pullair from between the electromagnet 10 and the structure 18 throughopenings in the guidepiece 26 that partially defines the opening 22closest to the structure 18, as designated by the arrows 74. Thus, asthe drilling tool 24 drills through the layers of material of thestructure 18, the debris 70 created by the drilling is pulled throughthe flutes of the drilling tool and from the hole 76 to the debriscollection container 66. Furthermore, the motion of removing thedrilling tool 24 from the hole 76 and the openings 22 and 30 facilitatesthe debris removal. Removing the debris 70 in this way therefore reducesthe risk that the debris 70 will accumulate in the hole 76 near orbetween the layers of the structure 18.

[0045] As FIG. 2 illustrates, the drilling tool 24, such as a drill bit,may be mounted to a countersink cage 25, referred to hereinafter as amicrostop countersink cage 25, and then mounted to a manual hand drillmotor 78. The drilling tool may be inserted through the openings 30and/or 22 once the electromagnet 10 has been energized and the debrisremoval system activated, if desired. Alternatively, any type of drillmotor 78 having a drill tool 24 may be used, such as any other manual orautomatic drills known to those skilled in the art. FIGS. 1 and 4illustrate one embodiment of the drilling tool 24 to create acountersunk hole 76, although other types of drilling tools may beutilized. The drilling tool 24 has a length sufficient to extend throughthe tooling platform 28, if applicable, and the electromagnet 10. Inaddition, the length is sufficient for the drilling tool 24 to extendthe desired amount into the structure 18 to create the desired hole.Thus, the drill tool 24 may have a shape such that a countersunk hole 76is created or a cylindrical hole is created.

[0046] If a countersunk hole 76 is desired, the drilling tool 24 has atip portion with a smaller diameter than the rearward portion of thetool. Thus, in order to ensure that the drill operator does not insertthe larger diameter portion of the drilling tool 24 into the structuretoo far, a microstop countersink cage 25 is advantageously positionedbetween the drill motor 78 and the drilling tool 24. The microstopcountersink cage 24 is calibrated to be positioned over the openings 30and/or 22 such that the microstop countersink cage 25 contacts thetooling platform 28, guidepiece 26, or the electromagnet 10, dependingupon the configuration, and prevents insertion of the drilling tool 24any further into the structure 18. The depth defined by contact of themicrostop countersink cage 25 generally permits the larger diameterrearward position to form a countersink proximate to one surface of thestructure and the smaller diameter tip portion to form a hole within,typically completely through the structure. Thus, the apparatus andmethod of the present invention permit a properly sized countersunk hole76 to be drilled in a structure in one operation, instead of having torevisit the hole after reassembling the layers and allowing the sealantto dry to drill the countersunk portion of the hole, as is the case inthe conventional process.

[0047] Once the properly sized hole 76 is drilled in the structure 18and longeron 58, if applicable, the drilling tool 24 may be removed andthe debris removal system deactivated. A fastener 80 may then beinserted into the hole. While the fastener 80 may be inserted by handafter deactivating and moving the electromagnet 10, the fastener 80 alsomay be inserted without moving the electromagnet 10 by a fastenerinsertion system directly through the opening 22 of the electromagnet10. The fastener insertion system generates air flow to carry thefastener 80 toward and into the hole 76. As shown in FIG. 5, air flow 82may be generated by an air flow generator 84. The air flow generator 84may be any type of air flow generator including a vacuum source or anair pump or fan, that generates air of a sufficient velocity to carrythe fastener 80. In addition, the air flow generator may be locatedanywhere relative to the hole 76 in order to create the desired airflow. In the shown embodiment, the air flow 82 is generated such that itflows through the opening 30 and/or 22 and/or hole 76. Thus, if the airflow generator 84 is a vacuum source, the vacuum source may be adaptedto create an air flow 82 as described above. Preferably, the generatedair flow is laminar. One example of the air flow generator 84 is theDF3-6 vacuum generator, commercially available from Vaccon Corp., whichprovides up to 393 feet/second maximum air velocity. The fastenerinsertion system may also include a seating 86 to contact theelectromagnet opening 22, or the platform opening 30, or the guide piece26 in embodiments in which the electromagnet 10 or the platform 28,respectively, still overlie the structure while the fastener 80 isinstalled. The seating 86 is a seal that reduces the amount of air thatescapes between the air flow generator 84 and the hole 76, and ensuresthe fastener 80 is carried to the hole 76 with the maximum amount of airvelocity.

[0048] The fastener insertion system may be aligned with and placeddirectly over the hole 76 or it may be aligned with and placed over thetooling platform opening 30, the electromagnet opening 22, or over theguidepiece 26 in embodiments in which the platform 28 or electromagnet10, respectively, still overlie the structures while the fastener 80 isinstalled. In embodiments that include a tooling platform 28, thefastener insertion system may be swivelably attached to the toolingplatform 28, as illustrated in FIGS. 6A and 6B. In the embodiment shownin FIGS. 6A and 6B, the fastener insertion system includes the air flowgenerator 84, the seating 86, and a tube 88 to facilitate insertion ofthe fastener 80 into the hole. The tube 88 may have circumferentialopenings that prevent the fastener 80 from inhibiting the air flow tothe air flow generator 84. Moreover, the tube 88 must be slightly largerin diameter than the fastener 80 to permit the fastener to passtherethrough.

[0049] The fastener insertion system may be attached to moveable arm 90,such that the arm 90 may move the fastener insertion system from theposition shown in FIG. 6A to the position shown in FIG. 6B. Thus, thefastener installation system may be in the position shown in FIG. 6Aduring drilling operations, and in the position shown in FIG. 6B duringfastener installation operations. The length of the arm 90 is such thatthe fastener insertion system may be aligned with the platform opening30 once in the position shown in FIG. 6B. The arm 90 may be connected tothe platform 28 via a hinge and movement may be activated by a motor 92.Any type of motor known to those skilled in the art that providessufficient power to move the arm 90 attached to the fastener insertionsystem in and out of position over the platform opening 30 may be used.One example of the motor 92 is a 24 VDC subfractional Hp gear motor. Themotor 92 may be activated by a switch, preferably located such that anoperator may easily reach it. In some embodiments, the switch also maycontrol power to the air flow generator 84, such that when the fastenerinsertion system is activated, the air flow generator 84 is actuated.Once the motor 92 moves the arm 90 and fastener insertion system intoposition over the platform opening 30, the backdrive of the motor iscompensated by switching to an alternate circuit that places a resistorin series to limit the current applied by the motor to the fastenerinsertion system and, therefore, hold the fastener insertion system inplace. The air flow generator 84 then may be activated and a fastener 80may be inserted into the tube 88. The air flow 82 carries the fastener80 toward and into the hole 76. After the fastener is inserted in thehole 76, a toggle switch for the motor 92 may be activated to move thearm 90 and the fastener insertion system away from the hole 76, to theposition shown in FIG. 6A.

[0050] If the size of the hole 76 is drilled to be a clearance fit withthe fastener 80, i.e. the diameter of the hole 76 is larger than thediameter of the fastener 80, then, after insertion, the fastener 80 maybe secured to the structure 18 in any manner known to those skilled inthe art such as by tightening a nut about a threaded portion of thefastener extending through the structure or by securing a collar on theportion of the fastener that extends through the structure. If the sizeof the hole 76 is drilled to be an interference fit with the fastener80, i.e., the diameter of the hole 76 is smaller than the diameter ofthe fastener 80, then the fastener will not be completely inserted intothe hole 76 after insertion. In this case, a fastener seating devicehaving a bar of sufficient length to extend through the platform opening30, if applicable, and the electromagnet opening 22 may be used to applyforce to the fastener 80 in order to completely insert the fastener 80into the hole 76. The fastener seating device may be any type of seatingdevice known to those skilled in the art, such as a rivet gun. Thefastener 80 is then ready to be secured to the structure 18 in anymanner known to those skilled in the art.

[0051] Thus, the apparatus and method of the present invention drillsholes and optionally inserts fasteners in a manner that reduces theamount of time, labor and cost involved in drilling holes inmultiple-layer structures and fastening the layers together. Byutilizing an electromagnet 10 and a clamp 12, the layers are heldtightly together to ensure that the layers will not separate as the tipof the drilling tool 24 impinges each layer and, as such, debris doesnot accumulate between the layers and exit burrs will not form. Thus,the layers do not have to be cleaned, de-burred and reassembled beforesealant can be applied, a countersink drilled, or a fastener insertedbecause the electromagnet 10 and clamp 12 assembly permit the layers tobe sealed prior to drilling, a countersunk hole to be drilled in onedrilling operation, and a fastener to be immediately inserted into thehole.

[0052] Many modifications and other embodiments of the inventions setforth herein will come to mind to one skilled in the art to which theseinventions pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the inventions are not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

That which is claimed:
 1. A method of drilling a hole in amultiple-layer structure, comprising: positioning an electromagnetproximate the structure such that an opening defined by theelectromagnet defines a location of the hole to be drilled in thestructure; positioning a clamp proximate the structure opposite theelectromagnet; energizing the electromagnet to securely hold themultiple layer structure together; positioning a drilling tool withinthe opening defined by the electromagnet; and drilling a hole in themultiple layer structure at the location defined by the opening definedby the electromagnet.
 2. The method of claim 1, further comprisingpositioning a template on the structure in the location to be drilled,wherein positioning the electromagnet comprises positioning theelectromagnet on the template such that the opening defined by theelectromagnet is aligned with an opening defined by the template.
 3. Themethod of claim 2, wherein the electromagnet comprises a guidepiecealigned with and partially defining the opening, and wherein positioningthe electromagnet on the template comprises positioning the guidepiecewithin the opening defined by the template to align the opening definedby the electromagnet with the opening defined by the template.
 4. Themethod of claim 1, wherein positioning the clamp comprises positioningthe clamp such that an opening defined by the clamp is aligned with theopening defined by the electromagnet
 5. The method of claim 1, furthercomprising: flowing air through the opening defined by theelectromagnet; and inserting a fastener into the hole drilled in themultiple-layer structure by pushing the fastener through the openingdefined by the electromagnet and into the hole drilled in themultiple-layer structure with the air.
 6. The method of claim 5, whereinflowing air through the opening defined by the electromagnet comprises:aligning a tube with the opening defined by the electromagnet; andpulling air through the tube.
 7. The method of claim 5, whereininserting the fastener comprises pulling the fastener through the tubeand pushing the fastener through the opening defined by theelectromagnet, and into the hole drilled in the multiple-layerstructure.
 8. The method of claim 5, wherein flowing air through theopening defined by the electromagnet comprises maintaining a laminar airflow through the opening defined by the electromagnet.
 9. The method ofclaim 1, wherein the clamp defines an opening, and wherein positioningthe clamp comprises receiving an indication from an indicator located onat least one of the electromagnet and the clamp that the openingsdefined by the electromagnet and the clamp are aligned.
 10. The methodof claim 1, wherein drilling a hole comprises drilling a hole having acountersunk portion.
 11. The method of claim 1, further comprisingsealing the multiple layers prior to positioning the electromagnet. 12.The method of claim 1, further comprising cooling the electromagnet withair flowing through the electromagnet at least during a portion of thetime that the electromagnet is energized.
 13. The method of claim 1,further comprising removing debris from the hole as the hole is drilledby creating air flow through the opening defined by the electromagnet ina direction away from the structure.
 14. The method of claim 1, whereinpositioning an electromagnet comprises normalizing the opening definedby the electromagnet to the portion of the structure to be drilled. 15.A method of inserting a fastener in a hole defined by a workpiece,comprising: aligning an opening defined by an insertion tube with thehole defined by the workpiece; generating air flow through the insertiontube in a direction toward the workpiece; placing the fastener into theinsertion tube; and carrying the fastener into the hole defined by theworkpiece as a result of the air flow through the tube.
 16. The methodof inserting a fastener of claim 15, wherein aligning the openingdefined by the insertion tube with the hole defined by the workpiececomprises aligning the opening defined by the insertion tube with anopening defined by a template that is placed on the workpiece such thatthe opening defined by the template is aligned with the hole defined bythe workpiece.
 17. The method of inserting a fastener of claim 15,further comprising controlling the air flow through the opening definedby the insertion tube.